1. Field of the Invention
The present invention relates to a battery separator and a battery, particularly, an alkaline battery separator and an alkaline primary or secondary battery containing the same.
2. Description of the Related Art
Separators have been used to separate the positive and negative electrodes of alkaline batteries for preventing short-circuits and holding the electrolyte to smoothly cause an electromotive reaction.
Hitherto, the separators of the alkaline secondary batteries were in the form of woven or nonwoven fabrics. The fibers constituting the woven or nonwoven fabric were generally polyamide fibers, and further, an alkaline electrolyte such as potassium hydroxide was used. Therefore, the fibers would become eroded away by the electrolyte with time, and short-circuiting would be caused between the positive and negative electrodes.
To avoid such defects, separators of polyolefin fibers such as polypropylene fibers were also used. Polyolefin fibers, however, are hydrophobic and lack in affinity with the electrolyte, so there was the problem of a poor electrolyte holding rate.
Further, even if separators of the above polyamide or polyolefin fiber were used, there still was the problem of short-circuiting caused by the deposition of branch-like metal crystals on the electrode plates, that is, dendrites, during discharging and/or charging, and therefore, a lifetime became shorter.
In the meanwhile, conventional alkaline primary battery separators were in the form of nonwoven fabrics, paper, or the like. The nonwoven fabrics or paper were generally made of vinylon or polyvinyl alcohol fibers, and an alkaline electrolyte such as potassium hydroxide was used. Therefore, the fibers would become eroded away by the electrolyte with time, and short-circuiting would be caused between the positive and negative electrode.
Further, mercerizated pulp, linter pulp or the like was used to enhance the electrolyte holding rate by the separator. However, the impurities contained in the pulp and/or aluminum added to the zinc constituting the negative electrode to prevent the generation of hydrogen in the electrolyte brought about the deposition of zinc oxide dendrites on the electrode plates to cause short-circuiting, then in turn cause an abnormal reduction of the voltage, and thus a lifetime became shorter.